This invention relates to a stapler for driving staples into an object, such as a sheaf of papers, said stapler comprising a base, a stapler head pivotably connected to the base via a first pin and pivotable between a starting position and a working position, in which it is applied against said object when this is placed in the stapler between the stapler head and the base, the stapler head being adapted to accommodate wire staple blanks which are juxtaposed and releasably interconnected to form at least one strip of staple blanks, a reciprocating staple shaper arranged in the stapler head to successively shape the staple blanks of the strip into substantially U-shaped staples, a reciprocating staple driver arranged in the stapler head to successively release the thus-formed staples from the strip and drive them into said object, an operating means which is pivotable about a second pin parallel to the first pin and which is adapted to reciprocate the staple shaper and the staple driver, and a drive means adapted to pivot the stapler head and the operating means in synchronism such that the operating means causes the staple driver, in a driving stroke, to drive a staple into said object and causes the staple shaper, in a shaping stroke, to shape the following staple, and such that the stapler head is pivoted to its working position before the staple driver performs the driving stroke, and is retained there during the driving stroke of the staple driver.
A prior-art stapler of this type is described in SE Patent Application 9201231-9. In this known stapler, the operating means is made up of two pivotable arms, which engage the staple shaper and the staple driver so as to reciprocate these during their pivotal movement. When the arms are being pivoted in the one direction, the staple shaper bends a staple blank into a U-shaped staple and the staple driver releases the U-shaped staple formed by the staple shaper during the preceding stapling cycle and drives it into the object at issue. While this is done, the stapler head is retained in its working position and is thus applied against the object.
In this known stapler, it is essential that the staple shaper completes the shaping stroke just as the staple driver completes the driving stroke, i.e., that the staple shaper and the staple driver reach their turning positions at exactly the same time. Should the staple shaper, as a result of dimensional imperfections, complete the shaping stroke before the staple driver has completed the driving stroke, the staple will not be driven into the object in its entirety, which of course is unacceptable. Should the staple driver complete the driving stroke, thus putting an end to the pivotal movement of the arms in said one direction, before the staple shaper has completed the shaping stroke, the resulting staple will be imperfectly shaped and will probably block up the stapler. Such premature ending of the driving stroke of the staple driver may, apart from dimensional imperfections, be due to a staple coming askew when it is be driven into the object, so that the staple is not driven into the object in its entirety but is deformed above it, thereby preventing completion of the driving stroke and, hence of the shaping stroke.